But having her on the 7th by c section :)
My due date is also the 12th of October
Go by ur period. Unless the US ur going by was the very 1st one and ur doc changed ur due also. If not all the other US are inaccurate for the dates. Ur period is the best bet.
Also, it's common to have the baby anytime from 2 weeks before to 2 weeks after your expected due date. It's just an estimate.
Generally go by last period, unless early ultrasounds showed something different. "Early" meaning before about 12 weeks. After that, the baby could have a growth spurt or something, so size isn't as good an indicator of age, or due date.